The present invention relates to new indoline derivatives which are suitable as UV absorbers, and to compositions which contain these UV absorbers to protect the skin from UV radiation.
The sun's radiation comprises, inter alia, the range of ultraviolet radiation which can be divided up into various ranges in respect of the action on the human skin:
(a) UV radiation of the wavelength range 285-320 nm (UVB range) causes sunburn (erythema) on people with normal skins, and this is followed by pigmentation based on photoinduced melanogenesis (indirect pigmentation). PA0 (b) UV radiation of the wavelength range 320-400 nm (UVA range) brings about rapid, but weakly developed browning (direct pigmentation). This pigmentation is based on photooxidation of certain precursors of melamine which are present in the skin. PA0 1. a high specific extinction E.sup.1 (which means: economy, less exposure to the formulation and a lower toxicological risk, since less is applied to the skin), PA0 2. excellent oil-solubility (no separation out at low temperatures, for example, during transport or use during winter sports), PA0 3. pH stability PA0 4. toxicological acceptability, and PA0 5. absence of pronounced intrinsic coloration. PA0 R.sup.2 and R.sup.3 are identical or different and denote C.sub.1 -C.sub.8 -alkyl; PA0 R.sup.10 denotes H or one or more C.sub.1 -C.sub.8 -alkyl, C.sub.1 -C.sub.8 -alkoxy, C.sub.5 -C.sub.6 -cycloalkyl, phenyl-C.sub.1 -C.sub.4 -alkyl or carb-C.sub.1 -C.sub.8 -alkoxy radicals, or halogen atoms. PA0 R.sup.5 =H, Alkyl, Halogen, Carboxyalkyl, Aryl, PA0 R=meaning as in formula I,
The conventional sunscreen agents contain UVB absorbers which absorb UVB radiation to a greater or lesser extent. However, for particularly light-sensitive people and in order to restrict the total exposure of the skin to UV radiation to a healthy level when the sun's radiation is more intense, there is a need for sunscreen agents which also contain substances absorbing UVA radiation (UVA absorbers).
Beyond the use in cosmetic sunscreen agents, UVA filters are of interest in dermatology for those products which can be used for the chemotherapy of chronic damage due to light, of psoriasis, and of occupational photodermatoses as may occur on dealing with tar, coal and pitch.
Furthermore, there are associations between the exposure of the skin to UVA radiation and its ageing. In addition, it is regarded as being certain that extensive exposure of the skin to UVA radiation signifies, especially when there is a genetically-based sensitivity, a greater risk of suffering from skin cancer. For these reasons, UVA absorbers are of particular significance for cosmetic and medical purposes.
The main requirements of such cosmetic UV absorbers are not their extreme stability to UV and heat as with UV absorbers for plastics, but, in particular:
It is a fact that, in principle, UVA absorbers for cosmetic purposes are not new. However, the known UVA absorbers do not adequately meet the conditions mentioned above, especially not with regard to the absorption maximum, the level of the specific extinction E.sup.1, and the oil-solubility.